// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/mm/nommu.c
 *
 *  Replacement code for mm functions to support CPU's that don't
 *  have any form of memory management unit (thus no virtual memory).
 *
 *  See Documentation/admin-guide/mm/nommu-mmap.rst
 *
 *  Copyright (c) 2004-2008 David Howells <dhowells@redhat.com>
 *  Copyright (c) 2000-2003 David McCullough <davidm@snapgear.com>
 *  Copyright (c) 2000-2001 D Jeff Dionne <jeff@uClinux.org>
 *  Copyright (c) 2002      Greg Ungerer <gerg@snapgear.com>
 *  Copyright (c) 2007-2010 Paul Mundt <lethal@linux-sh.org>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <generated/deconfig.h> 
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/sched/mm.h>
#include <linux/vmacache.h>
#include <linux/mman.h>
#include <linux/swap.h>
#include <linux/file.h>
#include <linux/highmem.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/blkdev.h>
#include <linux/backing-dev.h>
#include <linux/compiler.h>
#include <linux/mount.h>
#include <linux/personality.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/audit.h>
#include <linux/printk.h>

#include <linux/uaccess.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include "internal.h"

void *high_memory;
EXPORT_SYMBOL(high_memory);
struct page *mem_map = NULL;
//unsigned long max_mapnr;
//EXPORT_SYMBOL(max_mapnr);
//unsigned long highest_memmap_pfn;
//int sysctl_nr_trim_pages = CONFIG_NOMMU_INITIAL_TRIM_EXCESS;
//int heap_stack_gap = 0;

//atomic_long_t mmap_pages_allocated;

EXPORT_SYMBOL(mem_map);

///* list of mapped, potentially shareable regions */
//static struct kmem_cache *vm_region_jar;
//struct rb_root nommu_region_tree = RB_ROOT;
//DECLARE_RWSEM(nommu_region_sem);

//const struct vm_operations_struct generic_file_vm_ops = {
//};

///*
// * Return the total memory allocated for this pointer, not
// * just what the caller asked for.
// *
// * Doesn't have to be accurate, i.e. may have races.
// */
//unsigned int kobjsize(const void *objp)
//{
//	struct page *page;

//	/*
//	 * If the object we have should not have ksize performed on it,
//	 * return size of 0
//	 */
//	if (!objp || !virt_addr_valid(objp))
//		return 0;

//	page = virt_to_head_page(objp);

//	/*
//	 * If the allocator sets PageSlab, we know the pointer came from
//	 * kmalloc().
//	 */
//	if (PageSlab(page))
//		return ksize(objp);

//	/*
//	 * If it's not a compound page, see if we have a matching VMA
//	 * region. This test is intentionally done in reverse order,
//	 * so if there's no VMA, we still fall through and hand back
//	 * PAGE_SIZE for 0-order pages.
//	 */
//	if (!PageCompound(page)) {
//		struct vm_area_struct *vma;

//		vma = find_vma(current->mm, (unsigned long)objp);
//		if (vma)
//			return vma->vm_end - vma->vm_start;
//	}

//	/*
//	 * The ksize() function is only guaranteed to work for pointers
//	 * returned by kmalloc(). So handle arbitrary pointers here.
//	 */
//	return page_size(page);
//}

///**
// * follow_pfn - look up PFN at a user virtual address
// * @vma: memory mapping
// * @address: user virtual address
// * @pfn: location to store found PFN
// *
// * Only IO mappings and raw PFN mappings are allowed.
// *
// * Returns zero and the pfn at @pfn on success, -ve otherwise.
// */
//int follow_pfn(struct vm_area_struct *vma, unsigned long address,
//	unsigned long *pfn)
//{
//	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
//		return -EINVAL;

//	*pfn = address >> PAGE_SHIFT;
//	return 0;
//}
//EXPORT_SYMBOL(follow_pfn);

//LIST_HEAD(vmap_area_list);

//void vfree(const void *addr)
//{
//	kfree(addr);
//}
//EXPORT_SYMBOL(vfree);

//void *__vmalloc(unsigned long size, gfp_t gfp_mask)
//{
//	/*
//	 *  You can't specify __GFP_HIGHMEM with kmalloc() since kmalloc()
//	 * returns only a logical address.
//	 */
//	return kmalloc(size, (gfp_mask | __GFP_COMP) & ~__GFP_HIGHMEM);
//}
//EXPORT_SYMBOL(__vmalloc);

//void *__vmalloc_node_range(unsigned long size, unsigned long align,
//		unsigned long start, unsigned long end, gfp_t gfp_mask,
//		pgprot_t prot, unsigned long vm_flags, int node,
//		const void *caller)
//{
//	return __vmalloc(size, gfp_mask);
//}

//void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask,
//		int node, const void *caller)
//{
//	return __vmalloc(size, gfp_mask);
//}

//static void *__vmalloc_user_flags(unsigned long size, gfp_t flags)
//{
//	void *ret;

//	ret = __vmalloc(size, flags);
//	if (ret) {
//		struct vm_area_struct *vma;

//		mmap_write_lock(current->mm);
//		vma = find_vma(current->mm, (unsigned long)ret);
//		if (vma)
//			vma->vm_flags |= VM_USERMAP;
//		mmap_write_unlock(current->mm);
//	}

//	return ret;
//}

//void *vmalloc_user(unsigned long size)
//{
//	return __vmalloc_user_flags(size, GFP_KERNEL | __GFP_ZERO);
//}
//EXPORT_SYMBOL(vmalloc_user);

//struct page *vmalloc_to_page(const void *addr)
//{
//	return virt_to_page(addr);
//}
//EXPORT_SYMBOL(vmalloc_to_page);

//unsigned long vmalloc_to_pfn(const void *addr)
//{
//	return page_to_pfn(virt_to_page(addr));
//}
//EXPORT_SYMBOL(vmalloc_to_pfn);

//long vread(char *buf, char *addr, unsigned long count)
//{
//	/* Don't allow overflow */
//	if ((unsigned long) buf + count < count)
//		count = -(unsigned long) buf;

//	memcpy(buf, addr, count);
//	return count;
//}

//long vwrite(char *buf, char *addr, unsigned long count)
//{
//	/* Don't allow overflow */
//	if ((unsigned long) addr + count < count)
//		count = -(unsigned long) addr;

//	memcpy(addr, buf, count);
//	return count;
//}

///*
// *	vmalloc  -  allocate virtually contiguous memory
// *
// *	@size:		allocation size
// *
// *	Allocate enough pages to cover @size from the page level
// *	allocator and map them into contiguous kernel virtual space.
// *
// *	For tight control over page level allocator and protection flags
// *	use __vmalloc() instead.
// */
//void *vmalloc(unsigned long size)
//{
//       return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM);
//}
//EXPORT_SYMBOL(vmalloc);

///*
// *	vzalloc - allocate virtually contiguous memory with zero fill
// *
// *	@size:		allocation size
// *
// *	Allocate enough pages to cover @size from the page level
// *	allocator and map them into contiguous kernel virtual space.
// *	The memory allocated is set to zero.
// *
// *	For tight control over page level allocator and protection flags
// *	use __vmalloc() instead.
// */
//void *vzalloc(unsigned long size)
//{
//	return __vmalloc(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
//}
//EXPORT_SYMBOL(vzalloc);

///**
// * vmalloc_node - allocate memory on a specific node
// * @size:	allocation size
// * @node:	numa node
// *
// * Allocate enough pages to cover @size from the page level
// * allocator and map them into contiguous kernel virtual space.
// *
// * For tight control over page level allocator and protection flags
// * use __vmalloc() instead.
// */
//void *vmalloc_node(unsigned long size, int node)
//{
//	return vmalloc(size);
//}
//EXPORT_SYMBOL(vmalloc_node);

///**
// * vzalloc_node - allocate memory on a specific node with zero fill
// * @size:	allocation size
// * @node:	numa node
// *
// * Allocate enough pages to cover @size from the page level
// * allocator and map them into contiguous kernel virtual space.
// * The memory allocated is set to zero.
// *
// * For tight control over page level allocator and protection flags
// * use __vmalloc() instead.
// */
//void *vzalloc_node(unsigned long size, int node)
//{
//	return vzalloc(size);
//}
//EXPORT_SYMBOL(vzalloc_node);

///**
// * vmalloc_32  -  allocate virtually contiguous memory (32bit addressable)
// *	@size:		allocation size
// *
// *	Allocate enough 32bit PA addressable pages to cover @size from the
// *	page level allocator and map them into contiguous kernel virtual space.
// */
//void *vmalloc_32(unsigned long size)
//{
//	return __vmalloc(size, GFP_KERNEL);
//}
//EXPORT_SYMBOL(vmalloc_32);

///**
// * vmalloc_32_user - allocate zeroed virtually contiguous 32bit memory
// *	@size:		allocation size
// *
// * The resulting memory area is 32bit addressable and zeroed so it can be
// * mapped to userspace without leaking data.
// *
// * VM_USERMAP is set on the corresponding VMA so that subsequent calls to
// * remap_vmalloc_range() are permissible.
// */
//void *vmalloc_32_user(unsigned long size)
//{
//	/*
//	 * We'll have to sort out the ZONE_DMA bits for 64-bit,
//	 * but for now this can simply use vmalloc_user() directly.
//	 */
//	return vmalloc_user(size);
//}
//EXPORT_SYMBOL(vmalloc_32_user);

//void *vmap(struct page **pages, unsigned int count, unsigned long flags, pgprot_t prot)
//{
//	BUG();
//	return NULL;
//}
//EXPORT_SYMBOL(vmap);

//void vunmap(const void *addr)
//{
//	BUG();
//}
//EXPORT_SYMBOL(vunmap);

//void *vm_map_ram(struct page **pages, unsigned int count, int node)
//{
//	BUG();
//	return NULL;
//}
//EXPORT_SYMBOL(vm_map_ram);

//void vm_unmap_ram(const void *mem, unsigned int count)
//{
//	BUG();
//}
//EXPORT_SYMBOL(vm_unmap_ram);

//void vm_unmap_aliases(void)
//{
//}
//EXPORT_SYMBOL_GPL(vm_unmap_aliases);

//void free_vm_area(struct vm_struct *area)
//{
//	BUG();
//}
//EXPORT_SYMBOL_GPL(free_vm_area);

//int vm_insert_page(struct vm_area_struct *vma, unsigned long addr,
//		   struct page *page)
//{
//	return -EINVAL;
//}
//EXPORT_SYMBOL(vm_insert_page);

//int vm_map_pages(struct vm_area_struct *vma, struct page **pages,
//			unsigned long num)
//{
//	return -EINVAL;
//}
//EXPORT_SYMBOL(vm_map_pages);

//int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
//				unsigned long num)
//{
//	return -EINVAL;
//}
//EXPORT_SYMBOL(vm_map_pages_zero);

///*
// *  sys_brk() for the most part doesn't need the global kernel
// *  lock, except when an application is doing something nasty
// *  like trying to un-brk an area that has already been mapped
// *  to a regular file.  in this case, the unmapping will need
// *  to invoke file system routines that need the global lock.
// */
//SYSCALL_DEFINE1(brk, unsigned long, brk)
//{
//	struct mm_struct *mm = current->mm;

//	if (brk < mm->start_brk || brk > mm->context.end_brk)
//		return mm->brk;

//	if (mm->brk == brk)
//		return mm->brk;

//	/*
//	 * Always allow shrinking brk
//	 */
//	if (brk <= mm->brk) {
//		mm->brk = brk;
//		return brk;
//	}

//	/*
//	 * Ok, looks good - let it rip.
//	 */
//	flush_icache_user_range(mm->brk, brk);
//	return mm->brk = brk;
//}

///*
// * initialise the percpu counter for VM and region record slabs
// */
//void __init mmap_init(void)
//{
//	int ret;

//	ret = percpu_counter_init(&vm_committed_as, 0, GFP_KERNEL);
//	VM_BUG_ON(ret);
//	vm_region_jar = KMEM_CACHE(vm_region, SLAB_PANIC|SLAB_ACCOUNT);
//}

///*
// * validate the region tree
// * - the caller must hold the region lock
// */
//#ifdef CONFIG_DEBUG_NOMMU_REGIONS
//static noinline void validate_nommu_regions(void)
//{
//	struct vm_region *region, *last;
//	struct rb_node *p, *lastp;

//	lastp = rb_first(&nommu_region_tree);
//	if (!lastp)
//		return;

//	last = rb_entry(lastp, struct vm_region, vm_rb);
//	BUG_ON(last->vm_end <= last->vm_start);
//	BUG_ON(last->vm_top < last->vm_end);

//	while ((p = rb_next(lastp))) {
//		region = rb_entry(p, struct vm_region, vm_rb);
//		last = rb_entry(lastp, struct vm_region, vm_rb);

//		BUG_ON(region->vm_end <= region->vm_start);
//		BUG_ON(region->vm_top < region->vm_end);
//		BUG_ON(region->vm_start < last->vm_top);

//		lastp = p;
//	}
//}
//#else
//static void validate_nommu_regions(void)
//{
//}
//#endif

///*
// * add a region into the global tree
// */
//static void add_nommu_region(struct vm_region *region)
//{
//	struct vm_region *pregion;
//	struct rb_node **p, *parent;

//	validate_nommu_regions();

//	parent = NULL;
//	p = &nommu_region_tree.rb_node;
//	while (*p) {
//		parent = *p;
//		pregion = rb_entry(parent, struct vm_region, vm_rb);
//		if (region->vm_start < pregion->vm_start)
//			p = &(*p)->rb_left;
//		else if (region->vm_start > pregion->vm_start)
//			p = &(*p)->rb_right;
//		else if (pregion == region)
//			return;
//		else
//			BUG();
//	}

//	rb_link_node(&region->vm_rb, parent, p);
//	rb_insert_color(&region->vm_rb, &nommu_region_tree);

//	validate_nommu_regions();
//}

///*
// * delete a region from the global tree
// */
//static void delete_nommu_region(struct vm_region *region)
//{
//	BUG_ON(!nommu_region_tree.rb_node);

//	validate_nommu_regions();
//	rb_erase(&region->vm_rb, &nommu_region_tree);
//	validate_nommu_regions();
//}

///*
// * free a contiguous series of pages
// */
//static void free_page_series(unsigned long from, unsigned long to)
//{
//	for (; from < to; from += PAGE_SIZE) {
//		struct page *page = virt_to_page(from);

//		atomic_long_dec(&mmap_pages_allocated);
//		put_page(page);
//	}
//}

///*
// * release a reference to a region
// * - the caller must hold the region semaphore for writing, which this releases
// * - the region may not have been added to the tree yet, in which case vm_top
// *   will equal vm_start
// */
//static void __put_nommu_region(struct vm_region *region)
//	__releases(nommu_region_sem)
//{
//	BUG_ON(!nommu_region_tree.rb_node);

//	if (--region->vm_usage == 0) {
//		if (region->vm_top > region->vm_start)
//			delete_nommu_region(region);
//		up_write(&nommu_region_sem);

//		if (region->vm_file)
//			fput(region->vm_file);

//		/* IO memory and memory shared directly out of the pagecache
//		 * from ramfs/tmpfs mustn't be released here */
//		if (region->vm_flags & VM_MAPPED_COPY)
//			free_page_series(region->vm_start, region->vm_top);
//		kmem_cache_free(vm_region_jar, region);
//	} else {
//		up_write(&nommu_region_sem);
//	}
//}

///*
// * release a reference to a region
// */
//static void put_nommu_region(struct vm_region *region)
//{
//	down_write(&nommu_region_sem);
//	__put_nommu_region(region);
//}

///*
// * add a VMA into a process's mm_struct in the appropriate place in the list
// * and tree and add to the address space's page tree also if not an anonymous
// * page
// * - should be called with mm->mmap_lock held writelocked
// */
//static void add_vma_to_mm(struct mm_struct *mm, struct vm_area_struct *vma)
//{
//	struct vm_area_struct *pvma, *prev;
//	struct address_space *mapping;
//	struct rb_node **p, *parent, *rb_prev;

//	BUG_ON(!vma->vm_region);

//	mm->map_count++;
//	vma->vm_mm = mm;

//	/* add the VMA to the mapping */
//	if (vma->vm_file) {
//		mapping = vma->vm_file->f_mapping;

//		i_mmap_lock_write(mapping);
//		flush_dcache_mmap_lock(mapping);
//		vma_interval_tree_insert(vma, &mapping->i_mmap);
//		flush_dcache_mmap_unlock(mapping);
//		i_mmap_unlock_write(mapping);
//	}

//	/* add the VMA to the tree */
//	parent = rb_prev = NULL;
//	p = &mm->mm_rb.rb_node;
//	while (*p) {
//		parent = *p;
//		pvma = rb_entry(parent, struct vm_area_struct, vm_rb);

//		/* sort by: start addr, end addr, VMA struct addr in that order
//		 * (the latter is necessary as we may get identical VMAs) */
//		if (vma->vm_start < pvma->vm_start)
//			p = &(*p)->rb_left;
//		else if (vma->vm_start > pvma->vm_start) {
//			rb_prev = parent;
//			p = &(*p)->rb_right;
//		} else if (vma->vm_end < pvma->vm_end)
//			p = &(*p)->rb_left;
//		else if (vma->vm_end > pvma->vm_end) {
//			rb_prev = parent;
//			p = &(*p)->rb_right;
//		} else if (vma < pvma)
//			p = &(*p)->rb_left;
//		else if (vma > pvma) {
//			rb_prev = parent;
//			p = &(*p)->rb_right;
//		} else
//			BUG();
//	}

//	rb_link_node(&vma->vm_rb, parent, p);
//	rb_insert_color(&vma->vm_rb, &mm->mm_rb);

//	/* add VMA to the VMA list also */
//	prev = NULL;
//	if (rb_prev)
//		prev = rb_entry(rb_prev, struct vm_area_struct, vm_rb);

//	__vma_link_list(mm, vma, prev);
//}

///*
// * delete a VMA from its owning mm_struct and address space
// */
//static void delete_vma_from_mm(struct vm_area_struct *vma)
//{
//	int i;
//	struct address_space *mapping;
//	struct mm_struct *mm = vma->vm_mm;
//	struct task_struct *curr = current;

//	mm->map_count--;
//	for (i = 0; i < VMACACHE_SIZE; i++) {
//		/* if the vma is cached, invalidate the entire cache */
//		if (curr->vmacache.vmas[i] == vma) {
//			vmacache_invalidate(mm);
//			break;
//		}
//	}

//	/* remove the VMA from the mapping */
//	if (vma->vm_file) {
//		mapping = vma->vm_file->f_mapping;

//		i_mmap_lock_write(mapping);
//		flush_dcache_mmap_lock(mapping);
//		vma_interval_tree_remove(vma, &mapping->i_mmap);
//		flush_dcache_mmap_unlock(mapping);
//		i_mmap_unlock_write(mapping);
//	}

//	/* remove from the MM's tree and list */
//	rb_erase(&vma->vm_rb, &mm->mm_rb);

//	__vma_unlink_list(mm, vma);
//}

///*
// * destroy a VMA record
// */
//static void delete_vma(struct mm_struct *mm, struct vm_area_struct *vma)
//{
//	if (vma->vm_ops && vma->vm_ops->close)
//		vma->vm_ops->close(vma);
//	if (vma->vm_file)
//		fput(vma->vm_file);
//	put_nommu_region(vma->vm_region);
//	vm_area_free(vma);
//}

///*
// * look up the first VMA in which addr resides, NULL if none
// * - should be called with mm->mmap_lock at least held readlocked
// */
//struct vm_area_struct *find_vma(struct mm_struct *mm, unsigned long addr)
//{
//	struct vm_area_struct *vma;

//	/* check the cache first */
//	vma = vmacache_find(mm, addr);
//	if (likely(vma))
//		return vma;

//	/* trawl the list (there may be multiple mappings in which addr
//	 * resides) */
//	for (vma = mm->mmap; vma; vma = vma->vm_next) {
//		if (vma->vm_start > addr)
//			return NULL;
//		if (vma->vm_end > addr) {
//			vmacache_update(addr, vma);
//			return vma;
//		}
//	}

//	return NULL;
//}
//EXPORT_SYMBOL(find_vma);

///*
// * find a VMA
// * - we don't extend stack VMAs under NOMMU conditions
// */
//struct vm_area_struct *find_extend_vma(struct mm_struct *mm, unsigned long addr)
//{
//	return find_vma(mm, addr);
//}

///*
// * expand a stack to a given address
// * - not supported under NOMMU conditions
// */
//int expand_stack(struct vm_area_struct *vma, unsigned long address)
//{
//	return -ENOMEM;
//}

///*
// * look up the first VMA exactly that exactly matches addr
// * - should be called with mm->mmap_lock at least held readlocked
// */
//static struct vm_area_struct *find_vma_exact(struct mm_struct *mm,
//					     unsigned long addr,
//					     unsigned long len)
//{
//	struct vm_area_struct *vma;
//	unsigned long end = addr + len;

//	/* check the cache first */
//	vma = vmacache_find_exact(mm, addr, end);
//	if (vma)
//		return vma;

//	/* trawl the list (there may be multiple mappings in which addr
//	 * resides) */
//	for (vma = mm->mmap; vma; vma = vma->vm_next) {
//		if (vma->vm_start < addr)
//			continue;
//		if (vma->vm_start > addr)
//			return NULL;
//		if (vma->vm_end == end) {
//			vmacache_update(addr, vma);
//			return vma;
//		}
//	}

//	return NULL;
//}

///*
// * determine whether a mapping should be permitted and, if so, what sort of
// * mapping we're capable of supporting
// */
//static int validate_mmap_request(struct file *file,
//				 unsigned long addr,
//				 unsigned long len,
//				 unsigned long prot,
//				 unsigned long flags,
//				 unsigned long pgoff,
//				 unsigned long *_capabilities)
//{
//	unsigned long capabilities, rlen;
//	int ret;

//	/* do the simple checks first */
//	if (flags & MAP_FIXED)
//		return -EINVAL;

//	if ((flags & MAP_TYPE) != MAP_PRIVATE &&
//	    (flags & MAP_TYPE) != MAP_SHARED)
//		return -EINVAL;

//	if (!len)
//		return -EINVAL;

//	/* Careful about overflows.. */
//	rlen = PAGE_ALIGN(len);
//	if (!rlen || rlen > TASK_SIZE)
//		return -ENOMEM;

//	/* offset overflow? */
//	if ((pgoff + (rlen >> PAGE_SHIFT)) < pgoff)
//		return -EOVERFLOW;

//	if (file) {
//		/* files must support mmap */
//		if (!file->f_op->mmap)
//			return -ENODEV;

//		/* work out if what we've got could possibly be shared
//		 * - we support chardevs that provide their own "memory"
//		 * - we support files/blockdevs that are memory backed
//		 */
//		if (file->f_op->mmap_capabilities) {
//			capabilities = file->f_op->mmap_capabilities(file);
//		} else {
//			/* no explicit capabilities set, so assume some
//			 * defaults */
//			switch (file_inode(file)->i_mode & S_IFMT) {
//			case S_IFREG:
//			case S_IFBLK:
//				capabilities = NOMMU_MAP_COPY;
//				break;

//			case S_IFCHR:
//				capabilities =
//					NOMMU_MAP_DIRECT |
//					NOMMU_MAP_READ |
//					NOMMU_MAP_WRITE;
//				break;

//			default:
//				return -EINVAL;
//			}
//		}

//		/* eliminate any capabilities that we can't support on this
//		 * device */
//		if (!file->f_op->get_unmapped_area)
//			capabilities &= ~NOMMU_MAP_DIRECT;
//		if (!(file->f_mode & FMODE_CAN_READ))
//			capabilities &= ~NOMMU_MAP_COPY;

//		/* The file shall have been opened with read permission. */
//		if (!(file->f_mode & FMODE_READ))
//			return -EACCES;

//		if (flags & MAP_SHARED) {
//			/* do checks for writing, appending and locking */
//			if ((prot & PROT_WRITE) &&
//			    !(file->f_mode & FMODE_WRITE))
//				return -EACCES;

//			if (IS_APPEND(file_inode(file)) &&
//			    (file->f_mode & FMODE_WRITE))
//				return -EACCES;

//			if (locks_verify_locked(file))
//				return -EAGAIN;

//			if (!(capabilities & NOMMU_MAP_DIRECT))
//				return -ENODEV;

//			/* we mustn't privatise shared mappings */
//			capabilities &= ~NOMMU_MAP_COPY;
//		} else {
//			/* we're going to read the file into private memory we
//			 * allocate */
//			if (!(capabilities & NOMMU_MAP_COPY))
//				return -ENODEV;

//			/* we don't permit a private writable mapping to be
//			 * shared with the backing device */
//			if (prot & PROT_WRITE)
//				capabilities &= ~NOMMU_MAP_DIRECT;
//		}

//		if (capabilities & NOMMU_MAP_DIRECT) {
//			if (((prot & PROT_READ)  && !(capabilities & NOMMU_MAP_READ))  ||
//			    ((prot & PROT_WRITE) && !(capabilities & NOMMU_MAP_WRITE)) ||
//			    ((prot & PROT_EXEC)  && !(capabilities & NOMMU_MAP_EXEC))
//			    ) {
//				capabilities &= ~NOMMU_MAP_DIRECT;
//				if (flags & MAP_SHARED) {
//					pr_warn("MAP_SHARED not completely supported on !MMU\n");
//					return -EINVAL;
//				}
//			}
//		}

//		/* handle executable mappings and implied executable
//		 * mappings */
//		if (path_noexec(&file->f_path)) {
//			if (prot & PROT_EXEC)
//				return -EPERM;
//		} else if ((prot & PROT_READ) && !(prot & PROT_EXEC)) {
//			/* handle implication of PROT_EXEC by PROT_READ */
//			if (current->personality & READ_IMPLIES_EXEC) {
//				if (capabilities & NOMMU_MAP_EXEC)
//					prot |= PROT_EXEC;
//			}
//		} else if ((prot & PROT_READ) &&
//			 (prot & PROT_EXEC) &&
//			 !(capabilities & NOMMU_MAP_EXEC)
//			 ) {
//			/* backing file is not executable, try to copy */
//			capabilities &= ~NOMMU_MAP_DIRECT;
//		}
//	} else {
//		/* anonymous mappings are always memory backed and can be
//		 * privately mapped
//		 */
//		capabilities = NOMMU_MAP_COPY;

//		/* handle PROT_EXEC implication by PROT_READ */
//		if ((prot & PROT_READ) &&
//		    (current->personality & READ_IMPLIES_EXEC))
//			prot |= PROT_EXEC;
//	}

//	/* allow the security API to have its say */
//	ret = security_mmap_addr(addr);
//	if (ret < 0)
//		return ret;

//	/* looks okay */
//	*_capabilities = capabilities;
//	return 0;
//}

///*
// * we've determined that we can make the mapping, now translate what we
// * now know into VMA flags
// */
//static unsigned long determine_vm_flags(struct file *file,
//					unsigned long prot,
//					unsigned long flags,
//					unsigned long capabilities)
//{
//	unsigned long vm_flags;

//	vm_flags = calc_vm_prot_bits(prot, 0) | calc_vm_flag_bits(flags);
//	/* vm_flags |= mm->def_flags; */

//	if (!(capabilities & NOMMU_MAP_DIRECT)) {
//		/* attempt to share read-only copies of mapped file chunks */
//		vm_flags |= VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC;
//		if (file && !(prot & PROT_WRITE))
//			vm_flags |= VM_MAYSHARE;
//	} else {
//		/* overlay a shareable mapping on the backing device or inode
//		 * if possible - used for chardevs, ramfs/tmpfs/shmfs and
//		 * romfs/cramfs */
//		vm_flags |= VM_MAYSHARE | (capabilities & NOMMU_VMFLAGS);
//		if (flags & MAP_SHARED)
//			vm_flags |= VM_SHARED;
//	}

//	/* refuse to let anyone share private mappings with this process if
//	 * it's being traced - otherwise breakpoints set in it may interfere
//	 * with another untraced process
//	 */
//	if ((flags & MAP_PRIVATE) && current->ptrace)
//		vm_flags &= ~VM_MAYSHARE;

//	return vm_flags;
//}

///*
// * set up a shared mapping on a file (the driver or filesystem provides and
// * pins the storage)
// */
//static int do_mmap_shared_file(struct vm_area_struct *vma)
//{
//	int ret;

//	ret = call_mmap(vma->vm_file, vma);
//	if (ret == 0) {
//		vma->vm_region->vm_top = vma->vm_region->vm_end;
//		return 0;
//	}
//	if (ret != -ENOSYS)
//		return ret;

//	/* getting -ENOSYS indicates that direct mmap isn't possible (as
//	 * opposed to tried but failed) so we can only give a suitable error as
//	 * it's not possible to make a private copy if MAP_SHARED was given */
//	return -ENODEV;
//}

///*
// * set up a private mapping or an anonymous shared mapping
// */
//static int do_mmap_private(struct vm_area_struct *vma,
//			   struct vm_region *region,
//			   unsigned long len,
//			   unsigned long capabilities)
//{
//	unsigned long total, point;
//	void *base;
//	int ret, order;

//	/* invoke the file's mapping function so that it can keep track of
//	 * shared mappings on devices or memory
//	 * - VM_MAYSHARE will be set if it may attempt to share
//	 */
//	if (capabilities & NOMMU_MAP_DIRECT) {
//		ret = call_mmap(vma->vm_file, vma);
//		if (ret == 0) {
//			/* shouldn't return success if we're not sharing */
//			BUG_ON(!(vma->vm_flags & VM_MAYSHARE));
//			vma->vm_region->vm_top = vma->vm_region->vm_end;
//			return 0;
//		}
//		if (ret != -ENOSYS)
//			return ret;

//		/* getting an ENOSYS error indicates that direct mmap isn't
//		 * possible (as opposed to tried but failed) so we'll try to
//		 * make a private copy of the data and map that instead */
//	}


//	/* allocate some memory to hold the mapping
//	 * - note that this may not return a page-aligned address if the object
//	 *   we're allocating is smaller than a page
//	 */
//	order = get_order(len);
//	total = 1 << order;
//	point = len >> PAGE_SHIFT;

//	/* we don't want to allocate a power-of-2 sized page set */
//	if (sysctl_nr_trim_pages && total - point >= sysctl_nr_trim_pages)
//		total = point;

//	base = alloc_pages_exact(total << PAGE_SHIFT, GFP_KERNEL);
//	if (!base)
//		goto enomem;

//	atomic_long_add(total, &mmap_pages_allocated);

//	region->vm_flags = vma->vm_flags |= VM_MAPPED_COPY;
//	region->vm_start = (unsigned long) base;
//	region->vm_end   = region->vm_start + len;
//	region->vm_top   = region->vm_start + (total << PAGE_SHIFT);

//	vma->vm_start = region->vm_start;
//	vma->vm_end   = region->vm_start + len;

//	if (vma->vm_file) {
//		/* read the contents of a file into the copy */
//		loff_t fpos;

//		fpos = vma->vm_pgoff;
//		fpos <<= PAGE_SHIFT;

//		ret = kernel_read(vma->vm_file, base, len, &fpos);
//		if (ret < 0)
//			goto error_free;

//		/* clear the last little bit */
//		if (ret < len)
//			memset(base + ret, 0, len - ret);

//	} else {
//		vma_set_anonymous(vma);
//	}

//	return 0;

//error_free:
//	free_page_series(region->vm_start, region->vm_top);
//	region->vm_start = vma->vm_start = 0;
//	region->vm_end   = vma->vm_end = 0;
//	region->vm_top   = 0;
//	return ret;

//enomem:
//	pr_err("Allocation of length %lu from process %d (%s) failed\n",
//	       len, current->pid, current->comm);
//	show_free_areas(0, NULL);
//	return -ENOMEM;
//}

///*
// * handle mapping creation for uClinux
// */
//unsigned long do_mmap(struct file *file,
//			unsigned long addr,
//			unsigned long len,
//			unsigned long prot,
//			unsigned long flags,
//			unsigned long pgoff,
//			unsigned long *populate,
//			struct list_head *uf)
//{
//	struct vm_area_struct *vma;
//	struct vm_region *region;
//	struct rb_node *rb;
//	vm_flags_t vm_flags;
//	unsigned long capabilities, result;
//	int ret;

//	*populate = 0;

//	/* decide whether we should attempt the mapping, and if so what sort of
//	 * mapping */
//	ret = validate_mmap_request(file, addr, len, prot, flags, pgoff,
//				    &capabilities);
//	if (ret < 0)
//		return ret;

//	/* we ignore the address hint */
//	addr = 0;
//	len = PAGE_ALIGN(len);

//	/* we've determined that we can make the mapping, now translate what we
//	 * now know into VMA flags */
//	vm_flags = determine_vm_flags(file, prot, flags, capabilities);

//	/* we're going to need to record the mapping */
//	region = kmem_cache_zalloc(vm_region_jar, GFP_KERNEL);
//	if (!region)
//		goto error_getting_region;

//	vma = vm_area_alloc(current->mm);
//	if (!vma)
//		goto error_getting_vma;

//	region->vm_usage = 1;
//	region->vm_flags = vm_flags;
//	region->vm_pgoff = pgoff;

//	vma->vm_flags = vm_flags;
//	vma->vm_pgoff = pgoff;

//	if (file) {
//		region->vm_file = get_file(file);
//		vma->vm_file = get_file(file);
//	}

//	down_write(&nommu_region_sem);

//	/* if we want to share, we need to check for regions created by other
//	 * mmap() calls that overlap with our proposed mapping
//	 * - we can only share with a superset match on most regular files
//	 * - shared mappings on character devices and memory backed files are
//	 *   permitted to overlap inexactly as far as we are concerned for in
//	 *   these cases, sharing is handled in the driver or filesystem rather
//	 *   than here
//	 */
//	if (vm_flags & VM_MAYSHARE) {
//		struct vm_region *pregion;
//		unsigned long pglen, rpglen, pgend, rpgend, start;

//		pglen = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
//		pgend = pgoff + pglen;

//		for (rb = rb_first(&nommu_region_tree); rb; rb = rb_next(rb)) {
//			pregion = rb_entry(rb, struct vm_region, vm_rb);

//			if (!(pregion->vm_flags & VM_MAYSHARE))
//				continue;

//			/* search for overlapping mappings on the same file */
//			if (file_inode(pregion->vm_file) !=
//			    file_inode(file))
//				continue;

//			if (pregion->vm_pgoff >= pgend)
//				continue;

//			rpglen = pregion->vm_end - pregion->vm_start;
//			rpglen = (rpglen + PAGE_SIZE - 1) >> PAGE_SHIFT;
//			rpgend = pregion->vm_pgoff + rpglen;
//			if (pgoff >= rpgend)
//				continue;

//			/* handle inexactly overlapping matches between
//			 * mappings */
//			if ((pregion->vm_pgoff != pgoff || rpglen != pglen) &&
//			    !(pgoff >= pregion->vm_pgoff && pgend <= rpgend)) {
//				/* new mapping is not a subset of the region */
//				if (!(capabilities & NOMMU_MAP_DIRECT))
//					goto sharing_violation;
//				continue;
//			}

//			/* we've found a region we can share */
//			pregion->vm_usage++;
//			vma->vm_region = pregion;
//			start = pregion->vm_start;
//			start += (pgoff - pregion->vm_pgoff) << PAGE_SHIFT;
//			vma->vm_start = start;
//			vma->vm_end = start + len;

//			if (pregion->vm_flags & VM_MAPPED_COPY)
//				vma->vm_flags |= VM_MAPPED_COPY;
//			else {
//				ret = do_mmap_shared_file(vma);
//				if (ret < 0) {
//					vma->vm_region = NULL;
//					vma->vm_start = 0;
//					vma->vm_end = 0;
//					pregion->vm_usage--;
//					pregion = NULL;
//					goto error_just_free;
//				}
//			}
//			fput(region->vm_file);
//			kmem_cache_free(vm_region_jar, region);
//			region = pregion;
//			result = start;
//			goto share;
//		}

//		/* obtain the address at which to make a shared mapping
//		 * - this is the hook for quasi-memory character devices to
//		 *   tell us the location of a shared mapping
//		 */
//		if (capabilities & NOMMU_MAP_DIRECT) {
//			addr = file->f_op->get_unmapped_area(file, addr, len,
//							     pgoff, flags);
//			if (IS_ERR_VALUE(addr)) {
//				ret = addr;
//				if (ret != -ENOSYS)
//					goto error_just_free;

//				/* the driver refused to tell us where to site
//				 * the mapping so we'll have to attempt to copy
//				 * it */
//				ret = -ENODEV;
//				if (!(capabilities & NOMMU_MAP_COPY))
//					goto error_just_free;

//				capabilities &= ~NOMMU_MAP_DIRECT;
//			} else {
//				vma->vm_start = region->vm_start = addr;
//				vma->vm_end = region->vm_end = addr + len;
//			}
//		}
//	}

//	vma->vm_region = region;

//	/* set up the mapping
//	 * - the region is filled in if NOMMU_MAP_DIRECT is still set
//	 */
//	if (file && vma->vm_flags & VM_SHARED)
//		ret = do_mmap_shared_file(vma);
//	else
//		ret = do_mmap_private(vma, region, len, capabilities);
//	if (ret < 0)
//		goto error_just_free;
//	add_nommu_region(region);

//	/* clear anonymous mappings that don't ask for uninitialized data */
//	if (!vma->vm_file &&
//	    (!IS_ENABLED(CONFIG_MMAP_ALLOW_UNINITIALIZED) ||
//	     !(flags & MAP_UNINITIALIZED)))
//		memset((void *)region->vm_start, 0,
//		       region->vm_end - region->vm_start);

//	/* okay... we have a mapping; now we have to register it */
//	result = vma->vm_start;

//	current->mm->total_vm += len >> PAGE_SHIFT;

//share:
//	add_vma_to_mm(current->mm, vma);

//	/* we flush the region from the icache only when the first executable
//	 * mapping of it is made  */
//	if (vma->vm_flags & VM_EXEC && !region->vm_icache_flushed) {
//		flush_icache_user_range(region->vm_start, region->vm_end);
//		region->vm_icache_flushed = true;
//	}

//	up_write(&nommu_region_sem);

//	return result;

//error_just_free:
//	up_write(&nommu_region_sem);
//error:
//	if (region->vm_file)
//		fput(region->vm_file);
//	kmem_cache_free(vm_region_jar, region);
//	if (vma->vm_file)
//		fput(vma->vm_file);
//	vm_area_free(vma);
//	return ret;

//sharing_violation:
//	up_write(&nommu_region_sem);
//	pr_warn("Attempt to share mismatched mappings\n");
//	ret = -EINVAL;
//	goto error;

//error_getting_vma:
//	kmem_cache_free(vm_region_jar, region);
//	pr_warn("Allocation of vma for %lu byte allocation from process %d failed\n",
//			len, current->pid);
//	show_free_areas(0, NULL);
//	return -ENOMEM;

//error_getting_region:
//	pr_warn("Allocation of vm region for %lu byte allocation from process %d failed\n",
//			len, current->pid);
//	show_free_areas(0, NULL);
//	return -ENOMEM;
//}

//unsigned long ksys_mmap_pgoff(unsigned long addr, unsigned long len,
//			      unsigned long prot, unsigned long flags,
//			      unsigned long fd, unsigned long pgoff)
//{
//	struct file *file = NULL;
//	unsigned long retval = -EBADF;

//	audit_mmap_fd(fd, flags);
//	if (!(flags & MAP_ANONYMOUS)) {
//		file = fget(fd);
//		if (!file)
//			goto out;
//	}

//	flags &= ~(MAP_EXECUTABLE | MAP_DENYWRITE);

//	retval = vm_mmap_pgoff(file, addr, len, prot, flags, pgoff);

//	if (file)
//		fput(file);
//out:
//	return retval;
//}

//SYSCALL_DEFINE6(mmap_pgoff, unsigned long, addr, unsigned long, len,
//		unsigned long, prot, unsigned long, flags,
//		unsigned long, fd, unsigned long, pgoff)
//{
//	return ksys_mmap_pgoff(addr, len, prot, flags, fd, pgoff);
//}

//#ifdef __ARCH_WANT_SYS_OLD_MMAP
//struct mmap_arg_struct {
//	unsigned long addr;
//	unsigned long len;
//	unsigned long prot;
//	unsigned long flags;
//	unsigned long fd;
//	unsigned long offset;
//};

//SYSCALL_DEFINE1(old_mmap, struct mmap_arg_struct __user *, arg)
//{
//	struct mmap_arg_struct a;

//	if (copy_from_user(&a, arg, sizeof(a)))
//		return -EFAULT;
//	if (offset_in_page(a.offset))
//		return -EINVAL;

//	return ksys_mmap_pgoff(a.addr, a.len, a.prot, a.flags, a.fd,
//			       a.offset >> PAGE_SHIFT);
//}
//#endif /* __ARCH_WANT_SYS_OLD_MMAP */

///*
// * split a vma into two pieces at address 'addr', a new vma is allocated either
// * for the first part or the tail.
// */
//int split_vma(struct mm_struct *mm, struct vm_area_struct *vma,
//	      unsigned long addr, int new_below)
//{
//	struct vm_area_struct *new;
//	struct vm_region *region;
//	unsigned long npages;

//	/* we're only permitted to split anonymous regions (these should have
//	 * only a single usage on the region) */
//	if (vma->vm_file)
//		return -ENOMEM;

//	if (mm->map_count >= sysctl_max_map_count)
//		return -ENOMEM;

//	region = kmem_cache_alloc(vm_region_jar, GFP_KERNEL);
//	if (!region)
//		return -ENOMEM;

//	new = vm_area_dup(vma);
//	if (!new) {
//		kmem_cache_free(vm_region_jar, region);
//		return -ENOMEM;
//	}

//	/* most fields are the same, copy all, and then fixup */
//	*region = *vma->vm_region;
//	new->vm_region = region;

//	npages = (addr - vma->vm_start) >> PAGE_SHIFT;

//	if (new_below) {
//		region->vm_top = region->vm_end = new->vm_end = addr;
//	} else {
//		region->vm_start = new->vm_start = addr;
//		region->vm_pgoff = new->vm_pgoff += npages;
//	}

//	if (new->vm_ops && new->vm_ops->open)
//		new->vm_ops->open(new);

//	delete_vma_from_mm(vma);
//	down_write(&nommu_region_sem);
//	delete_nommu_region(vma->vm_region);
//	if (new_below) {
//		vma->vm_region->vm_start = vma->vm_start = addr;
//		vma->vm_region->vm_pgoff = vma->vm_pgoff += npages;
//	} else {
//		vma->vm_region->vm_end = vma->vm_end = addr;
//		vma->vm_region->vm_top = addr;
//	}
//	add_nommu_region(vma->vm_region);
//	add_nommu_region(new->vm_region);
//	up_write(&nommu_region_sem);
//	add_vma_to_mm(mm, vma);
//	add_vma_to_mm(mm, new);
//	return 0;
//}

///*
// * shrink a VMA by removing the specified chunk from either the beginning or
// * the end
// */
//static int shrink_vma(struct mm_struct *mm,
//		      struct vm_area_struct *vma,
//		      unsigned long from, unsigned long to)
//{
//	struct vm_region *region;

//	/* adjust the VMA's pointers, which may reposition it in the MM's tree
//	 * and list */
//	delete_vma_from_mm(vma);
//	if (from > vma->vm_start)
//		vma->vm_end = from;
//	else
//		vma->vm_start = to;
//	add_vma_to_mm(mm, vma);

//	/* cut the backing region down to size */
//	region = vma->vm_region;
//	BUG_ON(region->vm_usage != 1);

//	down_write(&nommu_region_sem);
//	delete_nommu_region(region);
//	if (from > region->vm_start) {
//		to = region->vm_top;
//		region->vm_top = region->vm_end = from;
//	} else {
//		region->vm_start = to;
//	}
//	add_nommu_region(region);
//	up_write(&nommu_region_sem);

//	free_page_series(from, to);
//	return 0;
//}

///*
// * release a mapping
// * - under NOMMU conditions the chunk to be unmapped must be backed by a single
// *   VMA, though it need not cover the whole VMA
// */
//int do_munmap(struct mm_struct *mm, unsigned long start, size_t len, struct list_head *uf)
//{
//	struct vm_area_struct *vma;
//	unsigned long end;
//	int ret;

//	len = PAGE_ALIGN(len);
//	if (len == 0)
//		return -EINVAL;

//	end = start + len;

//	/* find the first potentially overlapping VMA */
//	vma = find_vma(mm, start);
//	if (!vma) {
//		static int limit;
//		if (limit < 5) {
//			pr_warn("munmap of memory not mmapped by process %d (%s): 0x%lx-0x%lx\n",
//					current->pid, current->comm,
//					start, start + len - 1);
//			limit++;
//		}
//		return -EINVAL;
//	}

//	/* we're allowed to split an anonymous VMA but not a file-backed one */
//	if (vma->vm_file) {
//		do {
//			if (start > vma->vm_start)
//				return -EINVAL;
//			if (end == vma->vm_end)
//				goto erase_whole_vma;
//			vma = vma->vm_next;
//		} while (vma);
//		return -EINVAL;
//	} else {
//		/* the chunk must be a subset of the VMA found */
//		if (start == vma->vm_start && end == vma->vm_end)
//			goto erase_whole_vma;
//		if (start < vma->vm_start || end > vma->vm_end)
//			return -EINVAL;
//		if (offset_in_page(start))
//			return -EINVAL;
//		if (end != vma->vm_end && offset_in_page(end))
//			return -EINVAL;
//		if (start != vma->vm_start && end != vma->vm_end) {
//			ret = split_vma(mm, vma, start, 1);
//			if (ret < 0)
//				return ret;
//		}
//		return shrink_vma(mm, vma, start, end);
//	}

//erase_whole_vma:
//	delete_vma_from_mm(vma);
//	delete_vma(mm, vma);
//	return 0;
//}
//EXPORT_SYMBOL(do_munmap);

//int vm_munmap(unsigned long addr, size_t len)
//{
//	struct mm_struct *mm = current->mm;
//	int ret;

//	mmap_write_lock(mm);
//	ret = do_munmap(mm, addr, len, NULL);
//	mmap_write_unlock(mm);
//	return ret;
//}
//EXPORT_SYMBOL(vm_munmap);

//SYSCALL_DEFINE2(munmap, unsigned long, addr, size_t, len)
//{
//	return vm_munmap(addr, len);
//}

///*
// * release all the mappings made in a process's VM space
// */
//void exit_mmap(struct mm_struct *mm)
//{
//	struct vm_area_struct *vma;

//	if (!mm)
//		return;

//	mm->total_vm = 0;

//	while ((vma = mm->mmap)) {
//		mm->mmap = vma->vm_next;
//		delete_vma_from_mm(vma);
//		delete_vma(mm, vma);
//		cond_resched();
//	}
//}

//int vm_brk(unsigned long addr, unsigned long len)
//{
//	return -ENOMEM;
//}

///*
// * expand (or shrink) an existing mapping, potentially moving it at the same
// * time (controlled by the MREMAP_MAYMOVE flag and available VM space)
// *
// * under NOMMU conditions, we only permit changing a mapping's size, and only
// * as long as it stays within the region allocated by do_mmap_private() and the
// * block is not shareable
// *
// * MREMAP_FIXED is not supported under NOMMU conditions
// */
//static unsigned long do_mremap(unsigned long addr,
//			unsigned long old_len, unsigned long new_len,
//			unsigned long flags, unsigned long new_addr)
//{
//	struct vm_area_struct *vma;

//	/* insanity checks first */
//	old_len = PAGE_ALIGN(old_len);
//	new_len = PAGE_ALIGN(new_len);
//	if (old_len == 0 || new_len == 0)
//		return (unsigned long) -EINVAL;

//	if (offset_in_page(addr))
//		return -EINVAL;

//	if (flags & MREMAP_FIXED && new_addr != addr)
//		return (unsigned long) -EINVAL;

//	vma = find_vma_exact(current->mm, addr, old_len);
//	if (!vma)
//		return (unsigned long) -EINVAL;

//	if (vma->vm_end != vma->vm_start + old_len)
//		return (unsigned long) -EFAULT;

//	if (vma->vm_flags & VM_MAYSHARE)
//		return (unsigned long) -EPERM;

//	if (new_len > vma->vm_region->vm_end - vma->vm_region->vm_start)
//		return (unsigned long) -ENOMEM;

//	/* all checks complete - do it */
//	vma->vm_end = vma->vm_start + new_len;
//	return vma->vm_start;
//}

//SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
//		unsigned long, new_len, unsigned long, flags,
//		unsigned long, new_addr)
//{
//	unsigned long ret;

//	mmap_write_lock(current->mm);
//	ret = do_mremap(addr, old_len, new_len, flags, new_addr);
//	mmap_write_unlock(current->mm);
//	return ret;
//}

//struct page *follow_page(struct vm_area_struct *vma, unsigned long address,
//			 unsigned int foll_flags)
//{
//	return NULL;
//}

//int remap_pfn_range(struct vm_area_struct *vma, unsigned long addr,
//		unsigned long pfn, unsigned long size, pgprot_t prot)
//{
//	if (addr != (pfn << PAGE_SHIFT))
//		return -EINVAL;

//	vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
//	return 0;
//}
//EXPORT_SYMBOL(remap_pfn_range);

//int vm_iomap_memory(struct vm_area_struct *vma, phys_addr_t start, unsigned long len)
//{
//	unsigned long pfn = start >> PAGE_SHIFT;
//	unsigned long vm_len = vma->vm_end - vma->vm_start;

//	pfn += vma->vm_pgoff;
//	return io_remap_pfn_range(vma, vma->vm_start, pfn, vm_len, vma->vm_page_prot);
//}
//EXPORT_SYMBOL(vm_iomap_memory);

//int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
//			unsigned long pgoff)
//{
//	unsigned int size = vma->vm_end - vma->vm_start;

//	if (!(vma->vm_flags & VM_USERMAP))
//		return -EINVAL;

//	vma->vm_start = (unsigned long)(addr + (pgoff << PAGE_SHIFT));
//	vma->vm_end = vma->vm_start + size;

//	return 0;
//}
//EXPORT_SYMBOL(remap_vmalloc_range);

//unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
//	unsigned long len, unsigned long pgoff, unsigned long flags)
//{
//	return -ENOMEM;
//}

//vm_fault_t filemap_fault(struct vm_fault *vmf)
//{
//	BUG();
//	return 0;
//}
//EXPORT_SYMBOL(filemap_fault);

//void filemap_map_pages(struct vm_fault *vmf,
//		pgoff_t start_pgoff, pgoff_t end_pgoff)
//{
//	BUG();
//}
//EXPORT_SYMBOL(filemap_map_pages);

//int __access_remote_vm(struct task_struct *tsk, struct mm_struct *mm,
//		unsigned long addr, void *buf, int len, unsigned int gup_flags)
//{
//	struct vm_area_struct *vma;
//	int write = gup_flags & FOLL_WRITE;

//	if (mmap_read_lock_killable(mm))
//		return 0;

//	/* the access must start within one of the target process's mappings */
//	vma = find_vma(mm, addr);
//	if (vma) {
//		/* don't overrun this mapping */
//		if (addr + len >= vma->vm_end)
//			len = vma->vm_end - addr;

//		/* only read or write mappings where it is permitted */
//		if (write && vma->vm_flags & VM_MAYWRITE)
//			copy_to_user_page(vma, NULL, addr,
//					 (void *) addr, buf, len);
//		else if (!write && vma->vm_flags & VM_MAYREAD)
//			copy_from_user_page(vma, NULL, addr,
//					    buf, (void *) addr, len);
//		else
//			len = 0;
//	} else {
//		len = 0;
//	}

//	mmap_read_unlock(mm);

//	return len;
//}

///**
// * access_remote_vm - access another process' address space
// * @mm:		the mm_struct of the target address space
// * @addr:	start address to access
// * @buf:	source or destination buffer
// * @len:	number of bytes to transfer
// * @gup_flags:	flags modifying lookup behaviour
// *
// * The caller must hold a reference on @mm.
// */
//int access_remote_vm(struct mm_struct *mm, unsigned long addr,
//		void *buf, int len, unsigned int gup_flags)
//{
//	return __access_remote_vm(NULL, mm, addr, buf, len, gup_flags);
//}

///*
// * Access another process' address space.
// * - source/target buffer must be kernel space
// */
//int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len,
//		unsigned int gup_flags)
//{
//	struct mm_struct *mm;

//	if (addr + len < addr)
//		return 0;

//	mm = get_task_mm(tsk);
//	if (!mm)
//		return 0;

//	len = __access_remote_vm(tsk, mm, addr, buf, len, gup_flags);

//	mmput(mm);
//	return len;
//}
//EXPORT_SYMBOL_GPL(access_process_vm);

///**
// * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
// * @inode: The inode to check
// * @size: The current filesize of the inode
// * @newsize: The proposed filesize of the inode
// *
// * Check the shared mappings on an inode on behalf of a shrinking truncate to
// * make sure that any outstanding VMAs aren't broken and then shrink the
// * vm_regions that extend beyond so that do_mmap() doesn't
// * automatically grant mappings that are too large.
// */
//int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
//				size_t newsize)
//{
//	struct vm_area_struct *vma;
//	struct vm_region *region;
//	pgoff_t low, high;
//	size_t r_size, r_top;

//	low = newsize >> PAGE_SHIFT;
//	high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;

//	down_write(&nommu_region_sem);
//	i_mmap_lock_read(inode->i_mapping);

//	/* search for VMAs that fall within the dead zone */
//	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, low, high) {
//		/* found one - only interested if it's shared out of the page
//		 * cache */
//		if (vma->vm_flags & VM_SHARED) {
//			i_mmap_unlock_read(inode->i_mapping);
//			up_write(&nommu_region_sem);
//			return -ETXTBSY; /* not quite true, but near enough */
//		}
//	}

//	/* reduce any regions that overlap the dead zone - if in existence,
//	 * these will be pointed to by VMAs that don't overlap the dead zone
//	 *
//	 * we don't check for any regions that start beyond the EOF as there
//	 * shouldn't be any
//	 */
//	vma_interval_tree_foreach(vma, &inode->i_mapping->i_mmap, 0, ULONG_MAX) {
//		if (!(vma->vm_flags & VM_SHARED))
//			continue;

//		region = vma->vm_region;
//		r_size = region->vm_top - region->vm_start;
//		r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;

//		if (r_top > newsize) {
//			region->vm_top -= r_top - newsize;
//			if (region->vm_end > region->vm_top)
//				region->vm_end = region->vm_top;
//		}
//	}

//	i_mmap_unlock_read(inode->i_mapping);
//	up_write(&nommu_region_sem);
//	return 0;
//}

///*
// * Initialise sysctl_user_reserve_kbytes.
// *
// * This is intended to prevent a user from starting a single memory hogging
// * process, such that they cannot recover (kill the hog) in OVERCOMMIT_NEVER
// * mode.
// *
// * The default value is min(3% of free memory, 128MB)
// * 128MB is enough to recover with sshd/login, bash, and top/kill.
// */
//static int __meminit init_user_reserve(void)
//{
//	unsigned long free_kbytes;

//	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);

//	sysctl_user_reserve_kbytes = min(free_kbytes / 32, 1UL << 17);
//	return 0;
//}
//subsys_initcall(init_user_reserve);

///*
// * Initialise sysctl_admin_reserve_kbytes.
// *
// * The purpose of sysctl_admin_reserve_kbytes is to allow the sys admin
// * to log in and kill a memory hogging process.
// *
// * Systems with more than 256MB will reserve 8MB, enough to recover
// * with sshd, bash, and top in OVERCOMMIT_GUESS. Smaller systems will
// * only reserve 3% of free pages by default.
// */
//static int __meminit init_admin_reserve(void)
//{
//	unsigned long free_kbytes;

//	free_kbytes = global_zone_page_state(NR_FREE_PAGES) << (PAGE_SHIFT - 10);

//	sysctl_admin_reserve_kbytes = min(free_kbytes / 32, 1UL << 13);
//	return 0;
//}
//subsys_initcall(init_admin_reserve);
